In the fall, I brought several of my favorite outdoor plants indoors in hopes they would survive over the winter and I would not have to buy all new plants for my outdoor pots and gardens. With temperatures in the 50’s in mid March, I started to wonder when and how to move my surviving plants back outside. (Yes, some did great but some did not do so well. I’ve learned some lessons about potting that should be beneficial during future attempts.) Of course, March is far too early to consider this move in any part of Minnesota. But when is the right time? And what are the tricks to assure a healthy transition?
This article is not intended to provide information on those plants that have been started from seed with the intent to transplant to your garden. However, much of this information does apply to them as well. If you are looking for a good resource regarding when specific vegetables should be started from seed and when they should be planted outdoors, the USDA provides schedules by zones.[i]
Even though data verifies that we are experiencing global warming, it is still recommended to wait until mid to late May to plant outdoors. Flowering annuals should not be planted until the chance of frost has passed.[ii] If you are uncertain when that is, the Department of Natural Resources provides a spring frost-free map for the state.[iii]
The plants had to adjust to the changed environment when they were moved indoors. The same holds true as they are moved outdoors. They will again have to accommodate changes in the amount of light, water, humidity and nutrients. The process of helping the plants adjust to these changes is referred to as “hardening”.
Begin the hardening process by bringing the plants outdoors about two weeks before you plan on actually replanting them. The plants should be placed outdoors in a shady area for a few hours. Steadily increase the amount of time they spend outdoors and increase the amount of sunlight. Also when they are first reintroduced to the outdoors, protect the plants from wind since this is another environmental condition that was not present indoors. Initially plants should also be protected from excessive rain. However, once they are re-acclimated and replanted, they will require more water than they did while in the house since they grow more rapidly outdoors. This also holds true for fertilizers . . . more is needed than when the plants were inside.
If the plants will remain in pots outdoors, add fresh potting mix to make up for that which has decomposed during the winter months.
If the plants will be transplanted to the garden, this should preferably occur on a cloudy day or later in the day so the hot sun will not negatively impact the plant.
Here is to a great growing season: beautiful flowers during spring, summer and fall, and a bumper crop of fruit and vegetables in the fall!!!!
Author: Linda Stein, Dakota County Master Gardener
[i] Zone 3-4 Planting Schedule, http://www.thevegetablegarden.info/resources/planting-schedules/zones-3-4-planting-schedule
[ii] Minnesota Yard and Garden News, April, 2010.